Process of making sodium ferrocyanid.



new and Improved Process of Makin UNITED STATES PATENT \OF'FICE- ALEXANDER R. TILLINGHAST, OI SOLVAY, NEW YORK, ASSIGNOB TO SEMET-SOLVAY COMPANY, OF SOLVAY, NEW YORK, A CORPORATION NEW YORK.

PROCESS OF MAKING SODIUM FERROCYANID.

No Drawing.

' To all whom it may'concern Be it known that I, ALEXANDER R. TIIr LINGHAST, a citizen of the UnitedStates, residing at Solvay, in the county of Onondaga and State of New York, have inventedS a diumFerrocyanid, of which the followmgis solution in sufficient quantit a specification.

As is well known, sodium ferrocyanid may be formed by effecting the combination with carbonate of iron and an alkali of hydrocyanic acid gas as obtained from the gases evolved in the destructive distillation of coal. A difliculty experienced in such a process is the loss of c anogen due to the formation, with ammonla of the gas, of ammonium ferroc'yanid. s,

The object of my improvementsis toobviate such loss and provide a means for producing the sodium ferrocyanid in other respects in a convenient and economical manner.

In carrying my process into efi'ect I first remove the ammonia constituent of the gas therefrom as completely as may be in any usual or convenient manner, as by causing the absorption of the ammonia in water. The gas containing the cyanogen is then scrubbed with water containing. ferrous carbonate, or its equivalent ferrous hydrate, in suspension and also soda ash (Na CO,) in to insure the alkalinity of the ferrous car onate. 'While .the carbonateof iron employed may bev ob a form it by dissolving in Water copperas and tained from any suitable source,'I prefer. -to

following reaction occurs:

Ferroushydrate is formed in substantiallyl soda ash. Upon agitating this mixture the the same manner b treating copperas wit 9 caustic soda. The errous carbonate is separated from the liquor either by settling out and decanting ofi the liquor or by filtration. The ferrous carbonate is then thoroughly washed until any remaining sulfate of soda is eliminated, whenfthe ferrous carbonate is I insoluble residue is allowed to settleout and ready for use."

The ferrous carbonate suspension is formed by agitating in Water approximately eight parts of ferrous carbonate with five parts of:

sodaash. Upon scrubbing the gas witlr this,

Specification of Letters Patent.

Application filed December 20, 1916. Serial No. 137,970.

'is then boiled and allowed to settle.

Patented Jan. 8, 1918.

reactions take as follows The liquor from the scrubber contains sodium ferrocyanid, which is in solution, soda ash in solution, probably all of which exists as bicarbonate of soda, a large excess of ferrous sulfid in the form of a black, insoluble sludge and a considerable quantit of .insolu le ammonia ferro-ferrocyani due to the presence of unseparated ammonia in the gas.

In order to convert this insoluble ferrocyanid, and anyother insoluble ferrocyanid that may be present, to the soluble form, milk of lime is added to the mixture wl ii plh,

e amount of lime added is such as is necessary to effect the desired reaction, 2'. ,e. onnn average from .1 to .5 of a pound of milk of lime to each gallon of liquor. The lime converts the bicarbonate and carbonate of soda present into caustic soda as follows;-

which in turn converts the insoluble ferrocyanids into soluble ferrocyanid as according to the reaction:

place which may be expressed Na, Fe on eunpue-reo' n, The addition of the milk of lime not only effects the conversion of the insoluble ferrothe clear liquor is'drawn ofi and concentrated to the point of crystallization after which it is run into pans and the ferrocyanid allowed to crystallize out.

In order to purify the product the crystals are separated from the mother liquor and again dissolved in water or mother liquor from the previous final crystallization after which the solution is concentrated to the required strength and the ferrocyanid is again allowed to crystallize on strin s, or other bases, suspended in the liquor. he finished crystals are removed from the strings, washed, drained and dried and are then ready for shipment.

. Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The process of forming sodium ferrocyanid from the cyano en content of gas resulting from the distillation of coal which consists in removing the ammonia from the gas, scrubbing the gas with a solution of soda ash having ferrous carbonate in suspension, treating the resulting solution with milk of lime so as to form caustic soda and convert insoluble ferrocyanids present into soluble ferrocyanid and finally separating the insoluble matter from the solution and crystallizing out the ferrocyan'id.

2. The process of forming sodium ferrocyanid from the c anogen content ofgas resulting from the distillation of coal which consists in scrubbing the gas with a solution of soda ash havln ferrous carbonate in suspension, treating t e resulting solution with milk of lime so as to form caustic soda and convert insoluble ferrocyanids into soluble ferrocyanid and finally separating the insoluble matter from the solution and crystallizing out the ferrocyanid.

3. The improvement in the process of formin sodium ferrocyanid which consists in treating a solution-containing soda ash in solution and insoluble ferrocyanid with milk of lime so as to convert the soda ash into caustic soda and thereby break up the insoluble ferrocyanid and form soluble ferrocyanid.

4. The improvement in the process of forming sodium ferrocyanid which consists in treating a solution containing sodium ferrocyanid and soda ash with milk of lime to convert the soda ash into more soluble caustic soda, separating the insoluble matter from the solution and finall crystallizing out the sodium ferrocyanid caving caustic soda in solution.

In testimony whereof I have affixed my signature, this 16th day of December 1916.

ALEXANDER- n. TILLINGHAST. 

